1. Field of the Invention
The present invention generally relates to paging receivers and, more particularly, to an apparatus and method for saving battery power of a paging receiver when receiving messages.
2. Description of the Related Art
A Post Office Code Standardization Advisory Group (POCSAG) system, which is one of the current protocols used for paging receivers, transmits data asynchronously. Another currently used protocol is the FLEX.TM. Paging Protocol by Motorola, which employs a high speed paging system that transmits data synchronously. Referring to FIG. 1A, a diagram of a prior art POCSAG protocol signal used in a paging receiver is shown. The transmission of POCSAG is of a digital format and begins with preamble data of 576 bits followed by a plurality of batch data (generally 30 to 60 batches) which consists of address and message codewords. Particularly, one batch begins with a 32-bit synchronization codeword ("word sync") followed by 8 frames each having 64 bits. Each frame has a duration equivalent to two codewords, i.e., a 32-bit address codeword and a 32-bit message codeword. Therefore, one batch consists of 544 bits of data, seventeen words of 32 bits.
Referring now to FIG. 1B, a structure of a combined channel with POCSAG and FLEX system having collapse information equal to 4, as well as an operating waveform BS of a conventional paging receiver at that channel is shown.
Generally, a conventional paging receiver of a paging system includes a radio frequency (RF) circuit which is repeatedly turned on and off at regular intervals in order to detect the presence or absence of a signal such as preamble data, for example, to detect an incoming message or call. Hence, the RF circuit of the paging receiver is energized irrespective of whether or not the paging receiver is receiving its corresponding signal. Consequently, power is unnecessarily expended thereby reducing the life of the battery of the paging receiver.